This invention relates to copper-based adsorbents adapted to adsorb: (1) CO with CO/Cu ratios greater than 1.0, and/or (2) olefins with olefin/Cu ratios greater than 1.0.
The ability of solids or solutions containing copper(I) compounds to reversibly adsorb (or absorb) CO has led to a vital and expanding industry--the preparation of high purity CO from synthesis gas. Until recently, it was believed that the limiting CO:Cu stoichiometry for any copper carbonyl was 1:1, as exemplified by the following reaction scheme for copper(I) chloride: ##STR1## The solid phase can be bulk, crystalline CuCl, small crystallites of CuCl dispersed on high-surface-area materials, or atomically dispersed CuCl on high-surface-area materials.
Several developments cast doubt on the above scheme and on the general notion that Cu.sup.+ can form only monocarbonyls. One development was the observation by Souma et al. in 15 Inorg. Chem. 968 (1976) that solutions of Cu.sub.2 O in neat HSO.sub.3 F, BF.sub.3 .cndot.H.sub.2 O, and other strong acids absorbed up to four equivalents of CO per equivalent of Cu; the exact stoichiometry being dependent on temperature and pressure. Based on these observations, IR and Raman spectra of these solutions were interpreted in terms of the following set of equilibria: ##STR2## None of these carbonyl complexes could be isolated as solids. For reasons that are not clear, other possible interpretations of the data, especially the existence of the dicarbonyl complex [Cu(CO).sub.2 ].sup.+, were not considered.
Meyer et al. in 117 J. Am. Chem. Soc. 4071 (1995) observed that free, gaseous Cu.sup.+ has an affinity for four CO molecules. Bond enthalpies for the Cu.sup.+ --CO, (CO)Cu.sup.+ --CO, (CO).sub.2 Cu.sup.+ --CO, and (CO).sub.3 Cu.sup.+ --CO bonds were determined to be 36(2), 41(1), 18(1), and 13(1) kcal mol.sup.B1, respectively.
More recently, one of the instant inventors (Steven H. Strauss) and his colleagues disclosed that the literature compound CuAsF.sub.6 will adsorb up to three equivalents of CO at pressures less than one atmosphere. See Rack et al. 35 Inorg. Chem. 277 (1996). Three distinct solid compounds were formed depending on the pressure--[Cu(CO)][AsF.sub.6 ], [Cu(CO).sub.2 ][AsF.sub.6 ], and [Cu(CO).sub.3 ][AsF.sub.6 ]--and were characterized by manometry and by IR and Raman spectroscopy. The formation of the dicarbonyl compound [Cu(CO).sub.2 ][AsF.sub.6 ] suggests that the complex [Cu(CO).sub.2 ].sup.+ is also present in Souma's system and that IR and Raman spectra of strongly acidic solutions containing [Cu(CO).sub.n ].sup.+ ions should be re-examined and re-interpreted.
Despite the foregoing developments, it is desired to provide additional copper (I) polycarbonyls.
It is also desired to provide a CO adsorbent comprising copper (I) compounds that adsorb in excess of one CO per copper to form copper (I) polycarbonyls.
It is further desired to provide a gas adsorption apparatus comprising a copper-based adsorbent that adsorbs in excess of one CO per copper to form copper (I) polycarbonyls.
It is still further desired to provide a method of more efficiently adsorbing CO to a copper-based adsorbent in a gas adsorption process.
In addition, it is desired to provide compositions adapted to adsorb olefins, a method for separating olefins from hydrocarbons and an apparatus adapted to practice the method.
All references cited herein are incorporated herein by reference in their entireties.